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########################################################################
##
## Copyright (C) 2008-2025 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## This file is part of Octave.
##
## Octave is free software: you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING. If not, see
## <https://www.gnu.org/licenses/>.
##
########################################################################
## -*- texinfo -*-
## @deftypefn {} {} comet (@var{y})
## @deftypefnx {} {} comet (@var{x}, @var{y})
## @deftypefnx {} {} comet (@var{x}, @var{y}, @var{p})
## @deftypefnx {} {} comet (@var{hax}, @dots{})
## Produce a simple comet style animation along the trajectory provided by
## the input coordinate vectors (@var{x}, @var{y}).
##
## If @var{x} is not specified it defaults to the indices of @var{y}.
##
## The speed of the comet may be controlled by @var{p}, which represents the
## time each point is displayed before moving to the next one. The default for
## @var{p} is @code{5 / numel (@var{y})}.
##
## If the first argument @var{hax} is an axes handle, then plot into this axes,
## rather than the current axes returned by @code{gca}.
## @seealso{comet3}
## @end deftypefn
function comet (varargin)
[hax, varargin, nargin] = __plt_get_axis_arg__ ("comet", varargin{:});
if (nargin == 0 || nargin > 3)
print_usage ();
endif
if (nargin == 1)
y = varargin{1};
x = 1:numel (y);
p = 5 / numel (y);
elseif (nargin == 2)
x = varargin{1};
y = varargin{2};
p = 5 / numel (y);
elseif (nargin == 3)
x = varargin{1};
y = varargin{2};
p = varargin{3};
endif
oldfig = [];
if (! isempty (hax))
oldfig = get (0, "currentfigure");
endif
unwind_protect
hax = newplot (hax);
limits = [min(x), max(x), min(y), max(y)];
num = numel (y);
dn = round (num/10);
hl = plot (x(1), y(1), "color", "r", "marker", "none",
x(1), y(1), "color", "g", "marker", "none",
x(1), y(1), "color", "b", "marker", "o");
axis (limits); # set manual limits to speed up plotting
## Initialize the timer
t = p;
timerid = tic ();
for n = 2:(num+dn)
m = n - dn;
m = max ([m, 1]);
k = min ([n, num]);
set (hl(1), "xdata", x(1:m), "ydata", y(1:m));
set (hl(2), "xdata", x(m:k), "ydata", y(m:k));
set (hl(3), "xdata", x(k), "ydata", y(k));
pause (t - toc (timerid));
t += p;
endfor
unwind_protect_cleanup
if (! isempty (oldfig))
set (0, "currentfigure", oldfig);
endif
end_unwind_protect
endfunction
%!demo
%! clf;
%! title ("comet() animation");
%! hold on;
%! t = 0:.1:2*pi;
%! x = cos (2*t) .* (cos (t).^2);
%! y = sin (2*t) .* (sin (t).^2);
%! comet (x, y, .05);
%! hold off;
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